Add example profiles and noisy sample GPX

Four profiles exercising each waveform and channel; all verified to parse
against the Profile schema. Sample GPX has realistic GPS elevation noise so
the smoothing path (FR-5.2) is actually tested.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

profiles/sine-overunders.yaml

@@ -0,0 +1,32 @@
+name: Sine over-unders
+description: >-
+  Warm-up ramp, then eight sinusoidal cycles oscillating either side of
+  threshold, then a cool-down. Power-channel, so the trainer holds the target
+  regardless of cadence.
+looping: false
+
+blocks:
+  # Ten-minute warm-up, 100 W rising to 200 W.
+  - type: ramp
+    channel: power
+    from: 100.0
+    to: 200.0
+    extent:
+      seconds: 600.0
+
+  # Eight two-minute cycles: 240 W mean, +/- 40 W.
+  - type: wave
+    channel: power
+    shape: sine
+    midpoint: 240.0
+    amplitude: 40.0
+    period:
+      seconds: 120.0
+    repeats: 8.0
+
+  # Five-minute cool-down.
+  - type: constant
+    channel: power
+    value: 120.0
+    extent:
+      seconds: 300.0